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thanks for all

how to "choose" the seting values to protect a motor, i mean is there a genral considerations or we have to make calculations? exemple of a motor : 50 Kw, 400 V.

hi overcurrent (51) protection. When we see 100 A 0.3 s. so why we talk about curve, but there is only a point

there is also a maximum velocity of the expansion of the spring when closing the valve, which is insured by limiting device in the control panel

Thank you for your answers. as we only have values ​​without Reference to any standard , i'm looking for a document that gives an explanation.

it's a hydraulic actuator the distance between the Christmas Tree and the control-panel is 50 meters

ssv : surface safety valve 15 s : is there a standard or is it a best practice or a company specification ?

hi What is the maximum time expected for SSV to close (by de-energize the hydraulic control of actuator) ?

thanks for your answers.

indeed , passing a direct current will magnetize the CT.

the earthing system (localy buried on field near motors) is not enough for desipation of fault?

it's LV , 3phase +ground, the cable is armored the earthing system is every where aroud the motor location. i thought the use of the metallic armoris enough to use a torus.

if you inject DC==> no induction

hi to feed a motor when should we use (exemple) 4g70 sqmm instead of 3x70?

hi is there a standard talking about the necessity to add an air tank accumulator for BDV or SDV?

hi the "fc" (coating deterioration factor) is used to find the final current density by using the formula : if = i *fc*A (where "if" is the final current density and "i" the initial value , A is the surface area). my ask is : initial current density is the value of bar surface ?

I am sorry to ask this question, but: what I do not understand is the value of the breakdown factor (in my sense) should produces a value bigger than 1 in a purpose to compensate the deterioretion of the coating by injecting more current!!!

hi is the DNV RPB401 recommended practice used for offshore only or also for onshore cathodic protection design? I'm thinking about the Coating breakdown factor. Fc=a+b*t is there any sense to use it in underground structures evenly coated (bottom tank ).

it's in project, the VFD and the motor( multiphase pump) will be for rent and i don't really know the kind of VFD, but we have to prepare the project of supplying the substation.

hi all In Order to supply a VFD system (400 KW) we should install a power transformer (60 KV / 5.5 KV). my question is : is there special consideration about that transformer regarding to harmonics caused by the VFD ? thanks.